//坐标转换
//WGS84：为一种大地坐标系，也是目前广泛使用的GPS全球卫星定位系统使用的坐标系。
//GCJ02：又称火星坐标系，是由中国国家测绘局制订的地理信息系统的坐标系统。由WGS84坐标系经加密后的坐标系
//BD09：为百度坐标系，在GCJ02坐标系基础上再次加密。其中bd09ll表示百度经纬度坐标，bd09mc表示百度墨卡托米制坐标。
//h5在微信浏览器里、uniapp是使用 gcj02 国测局坐标系
//WGS84  GCJ02  BD09
const PI = 3.14159265358979324;
const x_pi = 3.14159265358979324 * 3000.0 / 180.0;
const delta = (lat, lon) => {
	// Krasovsky 1940
	//
	// a = 6378245.0, 1/f = 298.3
	// b = a * (1 - f)
	// ee = (a^2 - b^2) / a^2;
	var a = 6378245.0; //  a: 卫星椭球坐标投影到平面地图坐标系的投影因子。
	var ee = 0.00669342162296594323; //  ee: 椭球的偏心率。
	var dLat = transformLat(lon - 105.0, lat - 35.0);
	var dLon = transformLon(lon - 105.0, lat - 35.0);
	var radLat = lat / 180.0 * PI;
	var magic = Math.sin(radLat);
	magic = 1 - ee * magic * magic;
	var sqrtMagic = Math.sqrt(magic);
	dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * PI);
	dLon = (dLon * 180.0) / (a / sqrtMagic * Math.cos(radLat) * PI);
	return {
		'lat': dLat,
		'lon': dLon
	};
}

//WGS-84 to GCJ-02
const gcj_encrypt = (wgsLat, wgsLon) => {
	if (outOfChina(wgsLat, wgsLon))
		return {
			'lat': wgsLat,
			'lon': wgsLon
		};

	var d = delta(wgsLat, wgsLon);
	return {
		'lat': wgsLat + d.lat,
		'lon': wgsLon + d.lon
	};
}
const WGS_To_gcj = (gcjLat, gcjLon) => {
	return gcj_encrypt(gcjLat, gcjLon);
}
//GCJ-02 to WGS-84
const gcj_decrypt_To_wgs = (gcjLat, gcjLon) => {
	if (outOfChina(gcjLat, gcjLon))
		return {
			'lat': gcjLat,
			'lon': gcjLon
		};

	var d = delta(gcjLat, gcjLon);
	return {
		'lat': gcjLat - d.lat,
		'lon': gcjLon - d.lon
	};
}

//GCJ-02 to WGS-84 exactly
const gcj_decrypt_exact = (gcjLat, gcjLon) => {
	var initDelta = 0.01;
	var threshold = 0.000000001;
	var dLat = initDelta,
		dLon = initDelta;
	var mLat = gcjLat - dLat,
		mLon = gcjLon - dLon;
	var pLat = gcjLat + dLat,
		pLon = gcjLon + dLon;
	var wgsLat, wgsLon, i = 0;
	while (1) {
		wgsLat = (mLat + pLat) / 2;
		wgsLon = (mLon + pLon) / 2;
		var tmp = gcj_encrypt(wgsLat, wgsLon)
		dLat = tmp.lat - gcjLat;
		dLon = tmp.lon - gcjLon;
		if ((Math.abs(dLat) < threshold) && (Math.abs(dLon) < threshold))
			break;

		if (dLat > 0) pLat = wgsLat;
		else mLat = wgsLat;
		if (dLon > 0) pLon = wgsLon;
		else mLon = wgsLon;

		if (++i > 10000) break;
	}
	//console.log(i);
	return {
		'lat': wgsLat,
		'lon': wgsLon
	};
}

//GCJ-02 to BD-09
const bd_encrypt = (gcjLat, gcjLon) => {
	var x = gcjLon,
		y = gcjLat;
	var z = Math.sqrt(x * x + y * y) + 0.00002 * Math.sin(y * x_pi);
	var theta = Math.atan2(y, x) + 0.000003 * Math.cos(x * x_pi);
	let bdLon = z * Math.cos(theta) + 0.0065;
	let bdLat = z * Math.sin(theta) + 0.006;
	return {
		'lat': bdLat,
		'lon': bdLon
	};
}
const gcj_encrypt_To_bd = (gcjLat, gcjLon) => {
	return bd_encrypt(gcjLat, gcjLon);
}
//BD-09 to GCJ-02
const bd_decrypt_To_gcj = (bdLat, bdLon) => {
	var x = bdLon - 0.0065,
		y = bdLat - 0.006;
	var z = Math.sqrt(x * x + y * y) - 0.00002 * Math.sin(y * x_pi);
	var theta = Math.atan2(y, x) - 0.000003 * Math.cos(x * x_pi);
	var gcjLon = z * Math.cos(theta);
	var gcjLat = z * Math.sin(theta);
	return {
		'lat': gcjLat,
		'lon': gcjLon
	};
}

//WGS-84 to Web mercator
//mercatorLat -> y mercatorLon -> x
const mercator_encrypt = (wgsLat, wgsLon) => {
	var x = wgsLon * 20037508.34 / 180.;
	var y = Math.log(Math.tan((90. + wgsLat) * PI / 360.)) / (PI / 180.);
	y = y * 20037508.34 / 180.;
	return {
		'lat': y,
		'lon': x
	};
	/*
	 if ((Math.abs(wgsLon) > 180 || Math.abs(wgsLat) > 90))
	 return null;
	 var x = 6378137.0 * wgsLon * 0.017453292519943295;
	 var a = wgsLat * 0.017453292519943295;
	 var y = 3189068.5 * Math.log((1.0 + Math.sin(a)) / (1.0 - Math.sin(a)));
	 return {'lat' : y, 'lon' : x};
	 //*/
}
// Web mercator to WGS-84
// mercatorLat -> y mercatorLon -> x
const mercator_decrypt = (mercatorLat, mercatorLon) => {
	var x = mercatorLon / 20037508.34 * 180.;
	var y = mercatorLat / 20037508.34 * 180.;
	y = 180 / PI * (2 * Math.atan(Math.exp(y * PI / 180.)) - PI / 2);
	return {
		'lat': y,
		'lon': x
	};
	/*
	 if (Math.abs(mercatorLon) < 180 && Math.abs(mercatorLat) < 90)
	 return null;
	 if ((Math.abs(mercatorLon) > 20037508.3427892) || (Math.abs(mercatorLat) > 20037508.3427892))
	 return null;
	 var a = mercatorLon / 6378137.0 * 57.295779513082323;
	 var x = a - (Math.floor(((a + 180.0) / 360.0)) * 360.0);
	 var y = (1.5707963267948966 - (2.0 * Math.atan(Math.exp((-1.0 * mercatorLat) / 6378137.0)))) * 57.295779513082323;
	 return {'lat' : y, 'lon' : x};
	 //*/
}
// two point's distance
const distance = (latA, lonA, latB, lonB) => {
	var earthR = 6371000.;
	var x = Math.cos(latA * PI / 180.) * Math.cos(latB * PI / 180.) * Math.cos((lonA - lonB) * PI / 180);
	var y = Math.sin(latA * PI / 180.) * Math.sin(latB * PI / 180.);
	var s = x + y;
	if (s > 1) s = 1;
	if (s < -1) s = -1;
	var alpha = Math.acos(s);
	var distance = alpha * earthR;
	return distance;
}
const outOfChina = (lat, lon) => {
	if (lon < 72.004 || lon > 137.8347)
		return true;
	if (lat < 0.8293 || lat > 55.8271)
		return true;
	return false;
}
const transformLat = (x, y) => {
	var ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * Math.sqrt(Math.abs(x));
	ret += (20.0 * Math.sin(6.0 * x * PI) + 20.0 * Math.sin(2.0 * x * PI)) * 2.0 / 3.0;
	ret += (20.0 * Math.sin(y * PI) + 40.0 * Math.sin(y / 3.0 * PI)) * 2.0 / 3.0;
	ret += (160.0 * Math.sin(y / 12.0 * PI) + 320 * Math.sin(y * PI / 30.0)) * 2.0 / 3.0;
	return ret;
}
const transformLon = (x, y) => {
	var ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * Math.sqrt(Math.abs(x));
	ret += (20.0 * Math.sin(6.0 * x * PI) + 20.0 * Math.sin(2.0 * x * PI)) * 2.0 / 3.0;
	ret += (20.0 * Math.sin(x * PI) + 40.0 * Math.sin(x / 3.0 * PI)) * 2.0 / 3.0;
	ret += (150.0 * Math.sin(x / 12.0 * PI) + 300.0 * Math.sin(x / 30.0 * PI)) * 2.0 / 3.0;
	return ret;
}

const getRad = (d) => {
	var PI = Math.PI;
	return d * PI / 180.0;
}
/**
 * 获取两个经纬度之间的距离
 * @param lat1 第一点的纬度
 * @param lng1 第一点的经度
 * @param lat2 第二点的纬度
 * @param lng2 第二点的经度
 * @returns {Number}
 */
const getDistance = (lat1, lng1, lat2, lng2) => {
	var radLat1 = getRad(lat1);
	var radLat2 = getRad(lat2);
	var a = radLat1 - radLat2;
	var b = getRad(lng1) - getRad(lng2);
	var s = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a / 2), 2) + Math.cos(radLat1) * Math.cos(radLat2) * Math.pow(Math.sin(
		b / 2), 2)));
	s = s * 6378.137;
	// EARTH_RADIUS;
	s = Math.round(s * 10000) / 10000;
	return s ;
}

module.exports = {
	bd_decrypt_To_gcj: bd_decrypt_To_gcj,
	gcj_decrypt_To_wgs: gcj_decrypt_To_wgs,

	gcj_encrypt_To_bd,
	getDistance,
	
	WGS_To_gcj,
}
